Chest AP is a radiography positioning projection of the Thorax. Anteroposterior upright chest projection. SID 72". The centering point is located level of T7, 3 to 4 inches (8 to 10 cm) below the jugular notch, at the midsagittal plane. The central ray is perpendicular to the long axis of the sternum, generally about 5° caudad, to the level of T7 and the center of the IR. Image-quality criteria include both lungs visualized in entirety, apex to costophrenic angles, on a supine or semierect AP, Bontrager expects only eight or nine posterior ribs above the diaphragm; ten is the erect PA minimum. A sample technique is 120 kVp with DR 1.6 or CR 3.2 mAs, at an SID of 72 inches (183 cm).
Watch the setup
All steps (3)
- Position patient upright facing the tube, back against the upright Bucky.
- Flex the elbows, pronate the hands and place them on the hips to draw the scapulae laterally; shoulders in the same transverse plane.
- Center the midsagittal plane to the IR; top of the IR 1.5 to 2 inches (4 to 5 cm) above the relaxed shoulders.
3D anatomy: BodyParts3D, © The Database Center for Life Science. Posed, rendered and labelled by RadTechPrepper. These animations are licensed CC BY-SA 4.0. Credits
Anatomy demonstrated
- Entire lungs from apex to costophrenic angle.
- Heart and mediastinum (with greater magnification than PA).
- Thoracic vertebrae and ribs.
- Air-filled trachea from T1 down.
- Diaphragm and costophrenic angles.
- Clavicles and sternoclavicular joints.
Patient preparation
- Verify patient identity using two identifiers.
- Remove all radiopaque objects from the chest area.
- Confirm pregnancy status for female patients of child-bearing age.
- Explain breathing instructions: inspiration on the second breath in, hold.
- Position patient upright facing the tube, back against the upright Bucky.
- Flex the elbows, pronate the hands and place them on the hips to draw the scapulae laterally; shoulders in the same transverse plane.
- Center the midsagittal plane to the IR; top of the IR 1.5 to 2 inches (4 to 5 cm) above the relaxed shoulders.
Position & centering point
Level of T7, 3 to 4 inches (8 to 10 cm) below the jugular notch, at the midsagittal plane.
Central ray
Perpendicular to the long axis of the sternum, generally about 5° caudad, to the level of T7 and the center of the IR.
Exposure / technique
- kVp
- 120
- mAs
- DR 1.6 / CR 3.2
- SID
- 72" (183 cm)
- Notes
- High-kVp technique. Grid strongly recommended. AP shows greater cardiac magnification than PA. Sample technique: DR 1.6 / CR 3.2 mAs at 120 kVp, 72 in SID, for a 22 cm part (Merrill's sample chart). Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Both lungs visualized in entirety, apex to costophrenic angles.
- On a supine or semierect AP, Bontrager expects only eight or nine posterior ribs above the diaphragm; ten is the erect PA minimum.
- Sternoclavicular joints equidistant from the spine (no rotation).
- Clavicles more horizontal than on a PA, with about 1 inch of the apices seen above them.
- Sharp diaphragm and vascular markings (no respiratory motion).
- Trachea visible in the midline.
Common errors
- 1 Excessive shoulder elevation tilts the mediastinum and obscures the apices.
- 2 Rotation of the body shifts one clavicle laterally off the midline.
- 3 Chin not raised enough causes superimposition of mandible over apices.
- 4 Inadequate inspiration elevates the diaphragm and crowds the lung bases.
- 5 Off-centered CR clips the lung apices or costophrenic angles.
- 6 Rotation leaves the sternal ends of the clavicles at unequal distances from the spine.
- 7 Upper collimation border too low, cutting off the apices.
Clinical indications
- Routine evaluation when PA positioning is not feasible.
- Pathology of the lungs, diaphragm and mediastinum.